The present invention relates to a system and method for determining a location selected by a user on a surface and providing information to the user that has been determined to be relative to that location. In particular the present invention relates to position detection devices that are able to detect positions on a surface of two and three dimensional objects that have complex shapes. Additionally it relates to position detection devices in which the object may be turned, rotated or otherwise manipulated relative to the rest of the position detection system. Further, the present invention relates to provision of a ground point on the pointing device to ground the user to the system to minimize noise input to the system processor and potential error in position identification.
A variety of technologies exist to determine the position of a stylus, or even a finger, placed on a surface. One technology is a grid of horizontal and vertical wires that are placed below the surface of a flat tablet or over the surface of a display device and emit position indicating signals which are detected by a stylus. Two devices using this type of technology are described in U.S. Pat. Nos. 5,149,919 and 4,686,332 to Greenias, et al. Applications using these devices are computer input drawing (or digitizing) tablets, and touch-screen display devices.
In another technology, surface acoustic waves are measured at the edges of a glass plate and are used to calculate the position on the plate that was selected by a finger or a stylus. Applications include high use touch screen kiosk displays where a conductive overlay technology would wear out.
Yet other technologies include the use of light pens as optical detectors. Additionally a frame around a flat display with an array of light emitters and detectors around the edge of the frame, may be used to detect when a finger or stylus is near the display surface. These technologies are limited to displays or flat surfaces.
Position detectors such as the devices disclosed in the Greanias patents, that use many conductors arranged in a grid, are not well suited to a complex shaped surface of either two or three dimensions. There are, at a minimum, difficulties in positioning and shaping the conductors to fit the contours of a complex shape.
Another similar device is a grid of horizontal and vertical wires placed over or beneath the surface of a flat display device that uses capacitive coupling of a stylus or finger. In this device, the capacitive coupling transfers position indicating signals from one wire to another which can be used to calculate the position of the coupling. Computer input tablets, as well as finger pointing mouse replacement tablets, use this technology.
In another technology, a rectangular homogenous transparent conductor is placed over the surface of a display device and bar contacts on the edges of the transparent conductor charge the conductor. Capacitive coupling of a stylus or a finger to the transparent conductor causes the conductor to discharge while sensors attached to the bar contacts measure the amount of current drawn through each of the contacts. Analysis of the ratios of the currents drawn from pairs of contacts on opposing sides of the rectangle provide an X-Y position on the panel that was selected by the user. A device of this type is described in U.S. Pat. No. 4,853,498 to Meadows, et al. An application of this device is a touch-screen display.
A similar technology uses a rectangular piece of extremely uniform resistive material with a series of discrete resistors along the edge and is mounted on a flat surface. A voltage differential is applied to the row of resistors on opposing sides of the rectangle and in a time-division manner the voltage differential is applied to the row of resistors of the other two opposing sides. The position indicating signals are either received by a stylus, or by a conductive overlay which can be depressed to contact the surface of the resistive material. One variety of this device is described in U.S. Pat. No. 3,798,370 to Hurst.
The devices described in U.S. Pat. Nos. 4,853,498 (Meadows, et al.) and 3,798,370 (Hurst) drive a homogenous rectangular resistive overlay with bar contacts or a string of resistors along each edge. These approaches rely upon the regular shape of a rectangle in order to work. The shape and placement of the contacts provide the means to detect portions of the surface within a rectangular subsection of the resistive material of the surface. Other simple shapes may also be feasible with bar and resistor string contacts but in complex shapes they can create areas that cannot be distinguished (e.g., shapes with concave edges such as a circle or ellipse can not be accommodated by either the Meadows or the Hurst approaches). The use of bar contacts or strings of resistors along substantially the entire edge of an object limits their usefulness on objects where the position on the entire surface needs to be detected. The locations directly beneath each bar electrode and between each bar or spot electrode and the edge of the object are not detectable in these devices.
The devices described in U.S. Pat. Nos. 4,853,499 (Meadows, et al.) and 3,798,370 (Hurst) do not take into consideration the effects of contact resistance. The resistance between the contacts and the homogenous resistive material may be substantial relative to the resistance of the homogenous material. Additionally the contact resistance may vary from electrode to electrode or change due to mechanical or environmental stress. The Meadows and Hurst devices rely on contacts of known, or constant resistance, which constrains the use of materials and contact approaches. Any variation in contact resistance or changes in contact resistance due to environmental factors are not accounted for and result in detection errors.
Further, Meadows loads the surface with a capacitively coupled stylus and determines position by measuring the current drawn from the driving circuits. The Meadows device requires four receiver circuits to accomplish this.
The Meadows device is susceptible to the effects of unwanted phantom styluses coupling to the surface. Phantom styluses such as rings or fingers may couple to the active surface instead of, or in addition to, the actual stylus. These phantom styluses cause detection errors because the changes that they also produce cause changes in the driving circuit.
In applications where the object containing the grid needs to be rotated, or the electronics and the object are physically spaced-apart from each other, a large number of conductors must be coupled to the system, or between the elements of the systems, through connection mechanisms that may allow rotation or other movements. Such cables for the systems of the prior art would be rather large and cumbersome. Further, connectors with a large number of contacts are expensive and reduce the overall reliability of any system that requires them. Contacts that allow rotation, such as slip rings or commutators, become prohibitively complex and expensive as the number of connections rises above a small number. Additionally, the multiple circuits required to drive grid arrays are complex and costly to manufacture. Acoustic wave detectors provide a rugged position detection mechanism but are costly to implement. Light wave detection mechanisms are limited to flat surfaces and are susceptible to dust and insects blocking the light paths. It is believed, however, that the present invention solves these problems.
In today""s modern environment there are many sources of electro-magnetic energy, both naturally occurring and man-made. Some examples of the sources of such energy in the earth""s atmosphere are static electricity, electrical storms, heat lightning, radiation from outer space, and man-made radio waves. Each of these acts and interacts with each other causing interference and background noise to each other, depending on the intensity of the background or interfering signal. Thus, as is well known in devices that utilize an antenna as a device to detect an input signal, these atmospheric signals may interfere with the ability to detect and receive a signal of interest. It is also known that in systems with a hand-held antenna probe, the human body acts as a larger antenna with a signal from the person holding that probe added to the signal of interest detected by the hand-held probe. That added signal, and the multiple frequencies that it includes is also known to potentially add a level of inaccuracy in such a system, if the desired signal can be detected at all. To overcome that unwanted interference many elaborate circuits have been devised to suppress those interference signals xe2x80x9cpicked-upxe2x80x9d by the human user from impacting the performance of the system.
The present invention includes various apparatus and methods for determining a user selected position on an electrographic sensor unit. In the most general terms the electrographic sensor unit of the present invention includes a layer of a conductive material having an electrical resistivity with K spaced apart contact points electrically interconnected therewith, a processor connected to the K spaced apart contacts and disposed to selectively apply a signal to N of the K contact points where N has an integer value of 3 to K, and a probe assembly, including a stylus or a flexible conductive layer placed over the layer, coupled to the processor, the stylus disposed to be positioned by a user in vicinity of the user selected position on the layer, or the user to point a finger at the flexible conductive layer. In turn, the stylus, or the flexible conductive layer receives signals from the layer when the contact points have signals selectively applied thereto by the processor with the user selected position being determinable by the processor from the signals received from the stylus, or flexible layer, each in relation to a similar excitation of (N-J) different pairs of the K contact points under control of the processor, where J is an integer of 2 to (Nxe2x88x921).
Additionally, where the electrographic sensor includes more than one conductive layers that are each electrically isolated from each other, in the most general sense M conductive layers, the present invention is also able to discern which of those layers contains the user selected position. Here, each layer has K spaced apart contact points electrically interconnected with the corresponding layer of conductive material where N of the K contact points on each layer are used to locate the user selected position and where N has an integer value of three to K. The processor is similarly disposed to selectively apply a signal to each of the N contact points of each of the M layers and to determine which of the M layers and position coordinates of the user selected position on the corresponding one of the M layers in cooperation with a means for detecting and delivering a signal from the user selected position on the selected layer of the electrographic sensor unit to the processor.
The identification of the selected layer is accomplished by sequentially applying a first selected signal to all of the K contact points on each of the M layers in turn and measuring a first measured signal at said user selected position for each of the M layers individually with the first measurement corresponding to each one of the M layers being the signal received by the means for detecting and delivering when all of the contact points on that layer has the first selected signal applied to that layer""s contact points.
Next, a second measured signal is measured at the user selected position on the user selected layer for each of the M layers with each of the K contact points on each of the M layers open circuited, followed by the subtraction of the second measured signal from the first measured signal for each of the M layers to form M difference values.
Those M difference values are then each compared against a preselected threshold value to determine which one of those M difference values is both greater than that selected threshold and which exceeds it by the greatest value. The layer associated with the difference value that satisfies those conditions is then identified as the layer that contains the user selected position. Then once that determination is made the coordinates of the user selected position on that layer can be determined as discussed above.
The present invention also includes techniques for compensating for contact resistance in each of the contact points on the conductive layer, as well as forming the conductive layer into a two or three dimensional shape which may be open or closed. Further, the present invention includes the placement of a conductive skin over the outer surface layer with that skin having a graphical representation thereon and the present invention having the capability to convert the position coordinates of the user selected position from the coordinates of the conductive layer to those of the graphical representation. Such a graphical representation may be that of a map or a globe, even a mythical map or one of a star or another planet. Carrying this one step further, those graphical coordinates may also be used to electronically deliver information that has been prestored in memory relative to the selected graphical coordinates to the user.
In actual application the present invention can take many forms from a conductive layer with or without a non-conductive layer thereon and a stylus for use by the user to select a position on the layer, to a multi-layer structure with a conductive bottom layer, a non-conductive compressible inner layer, and a flexible conductive top layer where the user presses the top layer toward the bottom layer and the point at which the top and bottom layers are closest together is determined to be the user selected position. Further, various designs are proposed wherein the actuation and measured signals are either AC of a selected frequency or DC.
The present invention also includes a probe assembly with a cable with two conductors. The proximate end conductor is coupled to the processor and the proximate end of the other conductor is connected to a signal neutral point. The stylus in turn is coupled to the cable and incorporates therein the distal ends of two conductors with the distal end of the conductor coupled to the processor disposed to receive signals from the layer when the contact points have signals selectively applied to them and the user positions the stylus in vicinity of a selected point on the surface. The distal end of the other conductor is disposed to be contacted by the user when holding the stylus to connect the user to the signal neutral point. To maximize the probability that the user holds the stylus making contact with the contact point, it is located externally and positioned to be contacted by the user during use of the stylus. Further improve that probability, and to increase the comfort of holding the stylus, an electrically conductive contact of a flexible conductive polymer is placed to encircle the stylus at a position to maximize the user""s comfort when holding the stylus.
Thus, to fully explain the scope of the present invention, a detailed discussion of various embodiments is offered in the Description of the Preferred Embodiments below. However it must be kept in mind that that discussion is not an exhaustive discussion and variations on the many themes that are presented are also considered to be part of the present invention.